A 51-year-old female was admitted to our hospital due to hemoptysis. Chest radiography revealed infiltrations in the middle lobe. Computed tomography (CT) of the thorax showed clusters of small nodules associated with a small cavity in the middle lobe, ligula and lower lobe of the right lung. Bronchiectasis was not detected. Transbronchial lung biopsy specimen (B4a) showed epithelioid cell granulomas with giant cells, and Mycobacterium avium was isolated in 4-week cultures of bronchial washings. This could be a case of early phase of pulmonary Mycobacterium avium complex infection in a patient without a so-called underlying condition. CT findings were characteristic and useful for the early diagnosis of MAC infection.